3a-Hydroxydesogestrel is a metabolite of desogestrel. Desogestrel is a molecule used in hormonal contraceptives. Most combined oral contraceptive pills (COCPs, or simply OCs) on the market today contain both an estrogen compound (ethinyl estradiol is common) plus a progestin (a progesterone-like compound) such as desogestrel. Desogestrel-containing birth control pills are sometimes referred to as 'third generation' oral contraceptives. In contrast, birth control pills that are considered 'second generation' (Tri-Levlen, for example) contain an estrogen and a progestin, but the progestin is different, such as levonorgestrel. (Wikipedia)